The prior art has employed many devices and systems to process and purify water from industrial operations and municipal sources prior to discharging the water. Activated-sludge wastewater treatment plants (WWTP's), which are well known in the art, have been most often utilized to address this problem. Additionally, many industrial and municipal water treatment plants utilize biological systems to pre-treat their wastes prior to discharging into the usual municipal treatment plant. In these processes, the microorganisms used in the activated sludge break down or degrade contaminants for the desired water treatment. Efficient process performance and control requires quick and accurate assessment of information on the activity of microorganisms. This has proven to be a difficult task in view of the wide variety of materials and contaminants that typically enter into treatment systems. Also, variations in the quantity of wastewater being treated, such as daily, weekly or seasonal changes, can dramatically change numerous important factors in the treatment process, such as pH, temperature, dissolved oxygen, nutrients and the like, alteration of which can be highly detrimental to proper wastewater treatment. Of course, improperly treated wastewater poses serious human health dangers.
Various biological nutrient removal (BNR) processes are currently being used in wastewater treatment plants to assist in contamination degradation. In a typical BNR process, contaminants in the wastewater, such as carbon sources (measured as biological oxygen demand or BOD), ammonia, nitrates, phosphates and the like are digested by the activated sludge in anaerobic, anoxic and aerobic stages, also known in the art. In the anaerobic stage, the wastewater, with or without passing through a preliminary settlement process, is mixed with return activated sludge (RAS), sometimes hereinafter referred to as "mixed liquor," discussed hereafter.
Certain microorganisms in the RAS are capable of rapid uptake of readily biodegradable carbon sources, such as short chain fatty acids and of forming storage products such as poly-.beta.-hydroxbutyrate (PHB) and poly-.beta.-hydroxyvalate (PHV). The energy for this process is provided by the hydrolysis of intracellular polyphosphates. As a result of an anaerobic selector, a large portion of available carbon sources are removed by the poly-P forming microorganisms, and PO.sup.-3.sub.4 is released into the water phase. The rapid uptake and storage of carbonaceous substrates by poly-P forming species of microorganisms insures proper phosphate removal in later oxic processes. It also denies access of other competing organisms to the limited amount of substrates available in the wastewater under anaerobic conditions.
In most wastewater treatment plants, one or several anoxic stages are arranged in the BNR process. In the anoxic stage, denitrifiers, i.e., microbial species capable of denitrification, utilize nitrate and/or nitrite as electron acceptors and consume some of the available carbon sources during the denitrification process. NO.sub.x is stepwisely reduced to nitrogen gas and released to the atmosphere in the following manner: EQU NO.sub.3.sup.- .fwdarw.NO.sub.2.sup.- .fwdarw.NO.fwdarw.N.sub.2 O.fwdarw.N.sub.2
The nitrate is usually supplied by recycling a certain volume of wastewater at the end of the oxic stage back to the beginning of the anoxic stage.
One or several oxic stages are typically employed in BNR processes. In the oxic stage, air containing about 20% oxygen or pure oxygen, is supplied so that a desired dissolved oxygen level is maintained. Autotrophic nitrifiers, i.e., microbial species capable of using ammonia as their energy source, convert ammonia to nitrite and nitrate under aerobic conditions. The poly-P microbial species in the wastewater uptake phosphate from the water phase and digest their intracellular PHB and PHV storage products converting it into polyphosphate, a compound for energy storage. The polyphosphate pool of the poly-P microbial species is thus replenished and phosphorous is removed from the water phase. The phosphorous is then removed from the system by sludge wasting, which is well known in the art. Under aerobic conditions, the remaining carbon sources in the water phase are further digested by aerobic organisms.